1. Field of the Invention
The present invention relates to a multiple-select multiplexer circuit, a semiconductor memory device including a multiplexer circuit, and a memory segment parallel test method of the semiconductor memory device.
2. Description of the Related Art
For example, wired OR logic is employed to form a multiplexer circuit, which selects one data line from several data lines provided in a semiconductor memory. In the wired OR logic, several drivers makes cascade connection with respect to one line (conducting path, interconnection). Two kinds, that is, domino circuit and tri-state buffer have been known as the driver.
In general, the wired OR logic using the domino circuit is composed of only NMOSFET having relatively small parasitic capacitance and high current driving capability. Thus, the high-speed operation is expected when multiple-input logic is formed. However, pre-charge and discharge operations are repeated in one-time logic operation; for this reason, current consumption becomes large, and also, cycle time becomes long.
On the other hand, the wired OR logic using the tri-state buffer has the problem described below. If an accident such as simultaneous select happens in the tri-state buffer, current exceeding 10 mA flows to a line in which several output nodes of the tri-state buffer are commonly connected. As a result, there is a possibility that damage is given to lines and semiconductor elements. In particular, if the foregoing accident happens in a burn-in operation such that high power supply voltage is applied, it is getting more and more serious.
JPN. PAT. APPLN. KOKAI Publication No. 2-235435 discloses the following configuration. According to the configuration, a tri-state buffer is added to an output buffer, and output nodes of the output and tri-state buffers makes wired OR connection. An output level detection circuit detects the output level of the output buffer, and the drive of the tri-state buffer is controlled in accordance with the detection result. By doing so, the driving capability is improved at the rise or fall period of the output waveform. However, the technique described in the Publication 2-235435 does not solve the problem peculiar to multiplexers although it enhances the rise or fall speed of the output waveform.